Decorative stone made of glass

ABSTRACT

Decorative stone made of glass with a facetted front and a mirrored rear converging from the periphery of the stone to a point provided with an adhesive ( 10 ), wherein the angle between opposite surfaces of the rear of the stone ( 1 ) is more than 150°.

[0001] The invention relates to a decorative stone made from glass with a facetted front, and a mirrored rear converging from the periphery of the stone to a point provided with an adhesive.

[0002] It has long been known (see GB 1 325 293) to provide glass decorative stones with an adhesive on the rear, so that they can be ironed individually or in the form of a pattern applied to transfer foils onto a textile substrate. In areas of application where ironing is inadvisable, in particular for imitation tattoos, pressure-sensitive adhesive is used instead of the usual hot-melt adhesive.

[0003] Decorative stones coated with adhesives basically have a planar rear, and the corresponding stone shape is known commercially as a rose. In exceptional cases in order to improve adhesion, stones with a concave rear have even been proposed (see WO 97/41746 and DE 26 46 727).

[0004] There is a need, per se, to configure stones of the type described in the introduction such that they can be attached to a substrate using an adhesive. This is the case in particular when the stones have on the front a planar central area (table) and their type of cut (“chaton”) thus resembles a diamond.

[0005] In the case of diamonds, a chaton normally has at the point of the stone an angle between 96° and 98°. In spite of the substantially different refractive index, with a glass stone an optical behaviour comparable to diamonds of a similar size is obtained. This is possible because the total reflection occurring on the rear of diamonds is replaced by mirroring.

[0006] Chatons with a standard angle have already been used occasionally on textile substrates, but this limited to very small stones with a diameter of less than 2.5 mm, and particularly soft substrates, as otherwise the gap between the periphery of the stone and substrate is too large.

[0007] If required, a certain increase in the diameter of adhesive chatons would be obtainable if the flattest of the chatons previously proposed were to be used, as have been described with an angle of 130°, and claimed for with an angle of up to 150° in AT 393 597. Larger stones have actually been used, however, configured with a flat rear, that is to say in rose form. In contrast to rivoli stones, when stones are chaton-cut, that is to say with a front table, this results in a central part that gives a less lively impression. Stones with a substantially increased brilliance are unexpectedly produced when the rear angle is made large enough for the adhesion of the stones no longer to be obstructed by the corresponding slight unevenness of the rear side of the stone. According to the invention, to this end it is provided that the angle between opposite rear surfaces of the stone is more than 150°.

[0008] Further details of the invention will be explained with reference to the drawings. In these there is shown, in

[0009] FIGS. 1 to 3 the flattest chaton described until now, from the rear, from the side, and from the front,

[0010] FIGS. 4 to 6 a first embodiment of a stone according to the invention,

[0011] FIGS. 7 to 9 a second embodiment represented in manner similar to FIGS. 1 to 3.

[0012] The known stone 1 shown in FIG. 1 is made of glass, preferably of glass with a high refractive index. As is usual in the case of stones that are sold commercially under the description of chatons, from the circular girdle 4, eight planar surfaces 8 come together to a point, which can be somewhat flattened into a culet 9. From the girdle 4 eight planar surfaces 2 extend forwards, terminating in the planar table 3 configured as a regular octagon.

[0013] What is unusual about the stone 1 shown is the angle of 130° between opposing surfaces 8 of the rear of the stone. Such an angle results in a completely different optical path for the incident light than is sought in conventional diamond cutting. It has been proved, however, that when the stone shown is used for manufacturing cup chains, the type of refraction of the light normally incident upon the table 3 is not vitally important. In contrast to an individual decorative stone that is worn perhaps as a pendant or ring, with a cup chain there are no preferred orientations for the mutual relationship of light source, stone and observer. This results in the individual stones always being in a position in which light already dispersed is reflected towards the observer.

[0014] With the stones according to the invention, however, which are designed for adhesion onto a substrate, it has to be assumed that the direction of observation is normal for the stones. The observer of a stone with a front table and planar rear (rose with chaton cut) thus sees less dispersed light, as, with a large diameter, the stone has relatively little brilliance. Faceting of the rear of the stone with an extremely large angle and thus an extremely low point on the rear of the stone is unexpectedly sufficient for substantially enlivening the stone. By means of this low point, it is possible to make the delimitation surface of the glue completely, or almost completely flat, and thus to make the adhesive invisible along the periphery of the stone. If a thickness of the adhesive of 0.3 mm is assumed in the proximity of the periphery of the stone, when the rear of the glue is completely planar, with a stone with 2 mm diameter, an angular field of approximately 150° and a peripheral angle of the facets of approximately 15°, with a stone diameter of 7 mm, an angular field of approximately 170°, with a peripheral angle of approximately 5°.

[0015] In the embodiment according to FIGS. 3 to 6, on the rear the stone has only one set of facets 8 that are inclined at an angle of approximately 5° to the central plane of the stone. These facets are covered with an adhesive 10, the thickness of which decreases towards the centre, so that the rear of the coated stone is completely planar. As the angle of inclination of the facets 8 is so slight, it would also be possible to use an adhesive 10 of constant thickness (thickness, for example, of 0.3 mm).

[0016] The embodiment according to FIGS. 7 to 9 differs from the embodiment according to FIGS. 4-6 in that a second set of facets 8′ is provided, that are opposite the facets 8. The large number of the surfaces thus present largely compensates for disadvantage of the slight inclination of the different surfaces. 

1. Decorative stone made of glass with a facetted front, and a mirrored rear converging from the periphery of the stone to a point and provided with an adhesive, characterised in that the angle between opposing surfaces (8 and 8′) of the rear of the stone (1) is more than 150°.
 2. Decorative stone according to claim 1, characterised in that the angle is more than 160°.
 3. Decorative stone according to claim 2, characterised in that the angle is between 170° and 175°.
 4. Decorative stone according to one of claims 1 to 3, characterised in that the rear of the stone is provided with two sets of planar surfaces (8 and 8′).
 5. Decorative stone according to one of claims 1 to 4, characterised in that the front of the stone is provided in the central area with a planar surface (table 3).
 6. Decorative stone according to one of claims 1 to 5, characterised in that the diameter of the stone is 2-7 mm.
 7. Decorative stone according to one of claims 1 to 6, characterised in that the rear of the adhesive (10) coated stone (1) is planar. 